Association mapping of drought tolerance and agronomic traits in rice (Oryza sativa L.) landraces

BACKGROUND

Asian cultivars were predominantly represented in global rice panel selected for sequencing and to identify novel alleles for drought tolerance. Diverse genetic resources adapted to Indian subcontinent were not represented much in spite harboring useful alleles that could improve agronomic traits, stress resilience and productivity. These rice accessions are valuable genetic resource in developing rice varieties suited to different rice ecosystem that experiences varying drought stress level, and at different crop stages. A core collection of rice germplasm adapted to Southwestern Indian peninsular genotyped using SSR markers and characterized by contrasting water regimes to associate genomic regions for physiological, root traits and yield related traits. Genotyping-By-Sequencing of selected accessions within the diverse panel revealed haplotype variation in genic content within genomic regions mapped for physiological, morphological and root traits.

RESULTS

Diverse rice panel (99 accessions) were evaluated in field and measurements on plant physiological, root traits and yield related traits were made over five different seasons experiencing varying drought stress intensity at different crop stages. Traits like chlorophyll stability index, leaf rolling, days to 50% flowering, chlorophyll content, root volume and root biomass were identified as best predictors of grain yield under stress. Association mapping revealed genetic variation among accessions and revealed 14 genomic targets associated with different physiological, root and plant production traits. Certain accessions were found to have beneficial allele to improve traits, plant height, root length and spikelet fertility, that contribute to the grain yield under stress. Genomic characterization of eleven accessions revealed haplotype variation within key genomic targets on chromosomes 1, 4, 6 and 11 for potential use as molecular markers to combine drought avoidance and tolerance traits. Genes mined within the genomic QTL intervals identified were prioritized based on tissue specific expression level in publicly available rice transcriptome data.

CONCLUSION

The genetic and genomic resources identified will enable combining traits with agronomic value to optimize yield under stress and hasten trait introgression into elite cultivars. Alleles associated with plant height, specific leaf area, root length from PTB8 and spikelet fertility and grain weight from PTB26 can be harnessed in future rice breeding program.

EGFR gene regulation in colorectal cancer cells by garlic phytocompounds with special emphasis on S-Allyl-L-Cysteine Sulfoxide

Colorectal cancer is one among the most common cancers in the world and a major cause of cancer related deaths. Similar to other cancers, colorectal carcinogenesis is often associated with over expression of genes related to cell growth and proliferation, especially Epidermal Growth Factor Receptor (EGFR). There is an increasing attention towards the plant derived compounds in prevention of colorectal carcinogenesis by downregulating EGFR. Among plants, garlic (Allium sativum L.) is emerging with anticancer properties by virtue of its organosulfur compounds. The present study was aimed to analyze the interaction ability of garlic compounds in the active region of EGFR gene by in silico molecular docking studies and in vitro validation. This was conducted using the Discovery studio software version 4.0. Among the tested compounds, s-allyl-l-cysteine-sulfoxide (SACS)/alliin showed higher affinity towards EGFR. Furthermore, wet lab analysis using cell viability test and EGFR expression analysis in colorectal cancer cells confirmed its efficacy as a potent anticancer agent.

Unusual discrimination against carrier protein antibodies during partial purification of hapten-protein polyclonal antibodies to plant stress hormones

Polyclonal antibodies (PcAb) were raised against t-zeatin riboside (t-ZR) and abscisic acid (ABA). t-ZR-BSA and ABA-BSA antibodies had high titre and specificity to haptens but also contained BSA specific antibodies as observed in double immuno diffusion and quantitative precipitation tests. Partial purification of antiserum by precipitation, desalting, and ion-exchange chromatography almost completely eliminated interference from BSA specific antibodies. Consequently, very little or no reaction was observed in dot-immunoblot assays even when high concentrations of BSA were probed with partially purified t-ZR-BSA IgG. Further studies with ABA antiserum showed that discrimination against BSA occurred during chromatography and not during salt fractionation. Because antibodies to both hapten and carrier protein were predominantly of IgG class, this unusual discrimination against carrier protein Ab was possibly influenced by two approaches followed for DEAE chromatography, viz. (i) adsorption of IgG at pH 8 followed by elution; or (ii) adsorption of contaminating proteins at neutral pH while specific IgG comes off as unbound fraction.